In recent years, a demand for a wide band antenna has been increased as a UWB wireless and the like have been widely used. However, a UWB (of not less than 3.1 GHz and not more than 10.6 GHz) stipulated by the FCC (Federal Communications Commission) includes a 5 GHz band (of not less than 5.15 GHz and not more than 5.85 GHz) used for a wireless LAN (IEEE802.11a). Accordingly, a wide band antenna used for the UWB wireless is requested not only to have a wide band property to cover the UWB but also to avoid interfering with the 5 GHz band.
A known antenna that meets such a request is exemplified by a patch antenna described in Patent Literature 1. The patch antenna described in Patent Literature 1 is configured to cover a wide band by providing a stub in an antenna element and providing a step in a ground plate. Furthermore, the patch antenna is configured to avoid interfering with a wireless LAN by providing a slit in the antenna element.
Furthermore, a known BRF (band reject filter) for a wireless station of a UWB system is exemplified by a BRF described in Patent Literature 2. The BRF described in Patent Literature 2 is configured such that a microstrip line has a nonuniform width so as to enhance a reflection coefficient in a specific band (a band in which interference should be avoided).